Actuators are used in myriad devices and systems. For example, many vehicles including, for example, aircraft, spacecraft, watercraft, and numerous other terrestrial and non-terrestrial vehicles, include one or more actuators to effect the movement of various control surfaces or components. In many applications, the actuators include power drive units, such as a motor, that are configured to receive a source of drive power to move an actuator element, and thus the control surfaces or components, to a commanded position.
When the power drive unit is implemented as a brushless DC motor, a motor rotational position sensor is typically included and is used to properly control motor commutation. Moreover, a second position sensor may additionally be provided to supply a position feedback signal representative of the actual component position. This position sensor may be associated with either the component itself or with the actuator. In many instances the position sensor is associated with the actuator, and may be implemented as an LVDT (linear variable differential transformer) or RVDT (rotary variable differential transformer).
Although the above-described configuration is generally safe, reliable, and robust, it can suffer certain drawbacks. For example, the second position sensor may be relatively expensive and thus cost prohibitive to system implementation, most notably if an LVDT or RVDT is used. However, component position can be a desirable parameter to determine in order to implement accurate closed-loop position control and to provide accurate position indication of the component. Hence, there is a need for determining the position of an actuator, or an actuated component 125, without incurring the potentially prohibitive cost that may be associated with providing a dedicated sensor for this function. The present invention addresses at least this need.